In the art of releasable or breakaway couplings for connecting a flexible fluid supply hose to another hose or fitting, for example, as disclosed in U.S. Pat. Nos. 3,719,194; 3,788,348; 4,617,975 and 4,674,525, it is common to use two mating valve bodies each of which encloses a spring-biased valve closure member. When the valve bodies are coupled together, both of the valve closure members are shifted to open positions against corresponding compression springs. When the valve bodies are separated, the closure members engage corresponding annular seats in order to close the fluid passages within the valve bodies. The valve bodies are releasably connected or coupled together by some means which fractures or releases when the valve bodies are subjected to a predetermined pulling force. As shown in above mentioned U.S. Pat. No. 4,617,975, such a force may be produced on the valve bodies when the coupling is used in a fuel supply hose extending to a dispensing nozzle, and the nozzle and hose are inadvertently pulled by a motor vehicle.
In some installations of a fuel supply system wherein a dispensing nozzle is connected by a flexible hose to a fuel pump, it has been found desirable to provide for collecting the fuel vapors which are emitted from a motor vehicle fuel tank as the tank is being filled with fuel. The vapors are sucked through a special dispensing nozzle which is connected to a coaxial fuel supply hose having an inner passage for supplying fuel and an outer annular passage for directing fuel vapor from the vehicle fuel tank back to the fuel dispensing pump. The reasons for returning the fuel vapor from the vehicle fuel tank to the fuel supply pump is to provide for a safer environment for the person dispensing the fuel into the tank and also to reduce pollution within the atmosphere.